1. Field of the Invention
The invention relates to methods of operating ground engaging implements, and to such implements, particularly but not exclusively pipeline ploughs and cable ploughs.
2. Description of the Related Art
A plough has been proposed in European Patent Publication No. 0010915 which is towed on the seabed by a surface vessel or by a submarine tractor using a tow member such as a wire. The tow member is connected to the plough at a hitch point above the landside of the plough or is connected to a point on a mechanism by which the tension in the tow member always acts effectively at a real or virtual hitch point above the landside. The plough is steered by forces which are reactions arising between the plough and an external surface. In particular, it is proposed to create such forces as reactions between the pipeline or cable and rollers on the plough or between ground and blades on angularly adjustable skids.
A drawback of those known proposals is that the forces available for steering are not controllable and are limited by external factors such as the need to impose only small loads on the pipeline or by the seabed conditions. Where the skids encounter rock, virtually no steering reaction can be derived and control of the plough could be difficult or impossible.